1. Field of the Invention
The invention relates to a device for detecting the positions of pivotable parts of a rail switch, such as, e.g., tongue rails by at least one sensor as well as a method for evaluating sensor signals with a view to determining the positions of pivotable parts of a rail switch.
2. Prior Art
Due to the ever increasing extension of high-speed lines for railways, demands on the check of rail switches are growing, in particular. In order to guarantee the safe operation of a railway, crossings of rail switches must take place at the highest degree of safety. To this end, it is absolutely necessary for the switch tongues to correctly assume, and also maintain, their end positions after having been pivoted by appropriate actuation drives. So far, tongue position detectors comprising mechanical end switches have been used to check these end positions. Yet, such mechanical devices are relatively complex and expensive, since they frequently are comprised of rod assemblies readily prone to damage and hence requiring frequent maintenance and readjustment. In addition to such mechanically operating position detectors, devices have become known which are comprised of inductively acting non-contact approximation switches.
From DE 35 11 891 A1 a device has become known, which consists of an electromotor-driven single-rail-switch actuator, a fixable adjustment slide and optionally a likewise fixable monitoring slide as well as a sensor arrangement for recognizing the end positions of the slides and their safeguarding states. By means of sensors integrated in such devices, the end positions are monitored and the locking position of the adjustment slide and optionally of the monitoring slide are recognized. The checking results are then transmitted to a control and monitoring lagic and/or a controlling interlocking installation while determining the practicability of the railway switch. No measurement of the distance between the tongue rail and the stock rail is provided.
From DE 26 36 359 A1, a device for monitoring the end positions of pivotable rails of railway switches has become known, wherein inductive switches are provided on defined control points and scanned by ferromagnetic counterparts arranged on the pivotable rail. By the inductively induced triggering of the switch, it is to be determined whether the pivotable rail has assumed its end position.
From EP 0 514 365 B1, a method for monitoring the state of rail switches and detecting premature wear in the region of the tongue rails of a rail switch has already been apparent. That method substantially aims at detecting by means of a sensor premature wear in the region of the tongue rail so as to store the smallest value of the distance between tongue rail and stock rail detected during crossing, while defining distance values and limit values in each case and comparing the same and triggering a maintenance signal upon exceeding of a defined limit value. Inductive or capacitive analog sensors are provided as potential approximation sensors.
Although such inductively acting approximation switches are very reliable and wear-free control elements, they cannot be used for continuously detecting the exact positions of the movable parts of a rail switch but are employed only for signalizing whether the tongue of a rail switch has reached the respective end position or not. Since inductively acting approximation switches are inserted in resonant circuits, the accuracy of any measurements is subject to the quality of the resonant circuit, which in turn strongly depends on external influences and on the accuracy of the structural components. It is, therefore, necessary to take expensive measures in order to enhance the redundancy and accuracy of such measuring devices.